An in-dash CD Player - often combined with radio tuner, WMA/MP3 player
An in-dash CD Receiver - with a multiple CD cassette / changer located elsewhere in the vehicle
Connect a portable CD player to an existing in-dash audio unit using either a cable and adapter or a bluetooth wireless connection.

Choosing a Car CD Player

The first two things to consider when choosing a car CD player are:

Will it physically fit into the vehicle
Will it integrate cosmetically with the dash and other electronics.

Physical Integration

Most decks have standardized form factors; so fit most cars, but there are exceptions, so make sure that the deck is suited for your car. You are usually pretty safe is the car stereo is made for the same market as the source of your car:

German made vehicles - the car sound systems standards are set by DIN, the German Institute for Standardization.

Japanese vehicles - standards are set by EIAJ; the Electronics Industry Association of Japan.

United States vehicles – guidelines set by SAE; Society of Automotive Engineers.

Some standard sizes are interchangeable, some not. Fit kits are commonly available; also called installation packages. The most common sizes are indicated by chassis size or codes:

at least four basic DIN sizes
one basic radio size
one size that fits only in certain GM and Chrysler vehicles.
a "double DIN" size common in many Japanese cars.

Most reputable mobile electronics retailers have guides that can tell if a particular stereo component or speaker will fit and if special modifications to your car or radio will be necessary.

Cosmetic integration

Does the faceplate and display match the rest of your dash? Some decks allow you to change the color of their displays.

Remote operation - if your car already has remote capability, identify whether the new deck integrates existing steering wheel functions or need custom integration.

Display – the display is the only way the device can communicate with you. Check you can read it in bright daylight; many displays wash out in bright surroundings making them almost useless. If the display is bright, check you can dim it to match the rest of your dash. Driving at night with a super bright display can be a driving hazard.

User controls – are buttons logically laid out for, easy to operate in one step to make use when driving safe. Check the owners manual makes sense!; many are translated badly from Koren or Japanese and are a game in themselves to make sense of.

Make use the off switch is the most obvious. It has been known to be left out of the button range and located deep in a hidden menu.

Media format support - Consider the media you want to play – XM or Sirius Satellite Radio, CD, MP3 discs, Multi-channel audio.

System Expansion Capability - A sub-woofer output is a must for many. Changer input — especially if it does not have MP3 long play capability. Check it doesn’t use the same port as used for satellite radio.

FM performance – if you are a radio fan, check modern units still perform well; many are now more concerned with alternative media at the expense of radio. Testing instore connected to a store demo board hooked to a cable or giant antennae is not representative of in-car performance. If you’re an AM talk radio fan, consider that also. Power supply impacts AM reception.

Sound – modern decks don’t suffer many sound quality issues, but if you like a particular sound-mix, check you can manipulate the required attributes.

Output voltage –most decks can be driven with less than a volt; modern decks outputs are more than 1 or 2 volts, so don’t expect problems here. Higher voltage outputs minimize noise problems, but good installation and proper wiring does more.

Warranty and support – check how long the warranty is and what it covers. Check it also applies if you install it yourself.

Basic CD Player Specifications

Understanding the basic specifications common to most car audio systems helps to compare makes and models and assess the likely in-car performance.

RMS Power Output: amount of continuous power the amplifier produces [in watts]. Higher RMS figures allow louder music, but not always better sound quality. Use RMS output to comparing receivers or amplifiers.
Peak Output: measures peak or maximum output, not a continuous rating. The output number is commonly found on the face of stereos and the front of many manufacturer components.
RMS Power Bandwidth: the frequency response or range used to determine the built-in amplifier's RMS power rating. Look for 20-20,000 Hz, the approximate range of human hearing.
Preamp Outputs: number of RCA output jacks on the rear of the receiver to connect external amps. The more the better.
Preamp Voltage: the stereo preamp output rating is only important if you are planning to add an external power amplifier. Look for over 2.0V.
FM Sensitivity: how well a receiver picks up FM radio signals. Smaller decibel femtowatts (dBf) values are better to pick up weaker stations.
Signal-to-Noise Ratio: measure of how well the unit silences background noise. Higher ratings indicate less noise.